What is the purpose and approach to functional status assessment in patient evaluation?

Functional Status Assessment in Patient Evaluation

Functional status assessment should utilize standardized measurement tools to objectively evaluate a patient's ability to perform activities of daily living (ADLs) and instrumental activities of daily living (IADLs), with the primary purpose of guiding treatment decisions, predicting outcomes, and monitoring disease progression. 1

Core Purpose of Functional Assessment

Functional status assessment serves multiple critical clinical functions that directly impact patient outcomes:

• Establishes baseline capabilities to set realistic treatment goals and document progression toward more complex functional levels 1
• Predicts mortality and morbidity, as functional capacity correlates strongly with survival across multiple disease states 1
• Guides treatment intensity decisions, particularly in determining candidacy for major interventions like cardiac transplantation or cancer therapy 1
• Identifies patients requiring rehabilitation intervention when poststroke or post-illness functional status falls below prestroke baseline 1

Assessment Approach: Disease-Specific Considerations

Cardiovascular Disease

For heart failure patients, direct measurement of peak oxygen consumption (peak VO₂) during cardiopulmonary exercise testing is the gold standard and should not be substituted with questionnaires or estimated exercise capacity. 1

• Peak VO₂ <10 mL/kg/min indicates accepted criteria for cardiac transplantation, while >15 mL/kg/min represents inadequate indication 1
• Resting ventricular function correlates poorly with exercise capacity, making functional testing essential 1
• The VE/VCO₂ slope ≥34 indicates abnormal ventilatory response and powerfully predicts mortality independent of peak VO₂ 1
• Ventilatory threshold (VT) provides effort-independent prognostic information when maximal effort is questionable 1

Critical pitfall: Symptom questionnaires and health status measures show only modest correlation with measured exercise capacity in heart failure and cannot substitute for direct VO₂ measurement, despite being quick and inexpensive 1

Stroke Rehabilitation

Use the Functional Independence Measure (FIM) as the standardized assessment tool for stroke patients, as mandated by VA facilities and recommended by the American Heart Association. 1

• Assessment must include both ADLs (basic functions for home independence) and IADLs (complex skills for community independence) 1
• Independence in IADLs associates with improved treatment tolerance and survival 1
• Communication assessment requires interview, conversation, observation, and standardized testing to identify both impairments and compensatory strategies 1

Oncology Patients

Comprehensive geriatric assessment (CGA) should evaluate functional status, comorbidities, cognition, psychological status, social support, and nutrition in elderly cancer patients, as these components independently predict treatment tolerance and survival. 1

• Three or more CGA deficits double the 5-year mortality rate regardless of cancer stage 1
• Lower ADL scores and malnutrition independently predict cancer treatment modifications 1
• The Vulnerable Elders Survey (VES-13) score ≥3 identifies patients at high risk for functional decline or death and can be completed quickly at home 1
• The "timed up and go" (TUG) test provides rapid mobility screening and predicts fall risk 1

Pulmonary Disease

Functional status in chronic respiratory disease should assess both functional capacity (maximal potential) and functional performance (actual daily activities), as walking may not be an important goal for up to one-third of patients. 1

• Use disease-specific tools like the Manchester Respiratory Activities of Daily Living Scale or London Chest Activity of Daily Living scale 1
• The Canadian Occupational Performance Measure (COPM) provides individualized assessment sensitive to patient-specific goals 1
• Anxiety and depression significantly worsen functional capacity independent of disease severity, warranting incorporation of stress management into rehabilitation 1

Measurement Tools and Interpretation

Objective Performance Measures

Exercise capacity below 5 METs predicts significant postoperative cardiac risk even without symptoms or ECG changes, while high exercise workload consistently predicts low risk. 1

• The 6-minute walk test provides standardized distance measurement correlating with outcomes 1
• Gait speed and other objective performance measures may reduce assessment bias compared to subjective performance status ratings 1

Patient-Reported Outcomes

While patient-reported outcome measures and activity monitoring devices (wearable technology) show promise, further research is needed to understand optimal incorporation into clinical practice 1. These tools may enhance objectivity and reduce bias in performance status assessments 1.

Clinical Implementation Strategy

Multidisciplinary assessment using standardized procedures should be documented for all patients requiring rehabilitation, with referral to specialist teams as soon as medical stability is achieved. 1

• Assessment takes minutes when using validated self-administered questionnaires that generate one-page computer-scored reports 2
• Functional assessment must evaluate aerobic capacity, cognition, balance, gait, motor function, muscle performance, pain, range of motion, and self-care abilities 1
• Psychosocial assessment by social workers should include families and caregivers, as early systematic discharge planning based on comprehensive assessment increases successful home return 1

Key caveat: Despite technical maturity of assessment tools with proven validity and reliability, widespread clinical adoption requires evidence that measurement actually enhances health outcomes, not just information content 3. The Tennessee Functional Status Questionnaire represents recent efforts to create brief, efficient tools standardized to METs that evaluate both performance and capacity while identifying contributors to functional decline 4.